The present invention relates to a low odor polyoxyalkylene polyol, a process for producing the same, and a low odor urethane prepolymer and a low odor urethane composition which use the polyoxyalkylene polyol as their raw materials.
Polyoxyalkylene polyol such as polypropylene glycol is widely used as a solvent or a synthetic raw material for a polyurethane or a modified silicone resin, but there has conventionally been the problem of its odor. This polyoxyalkylene polyol is generally obtained by ring opening addition polymerization of an alkylene oxide (epoxide) using a polyol such as ethylene glycol, glycerin or sucrose, as a polymerization initiator. However, odor of polyoxyalkylene polyol varies depending on a solvent, a catalyst or the like used in the course of the production. Methods of avoiding odor of polyoxyalkylene polyol when producing the same have conventionally been proposed. For example, a method of using polyoxyalkylene polyol in place of dimethylformamide (DMF) in order to avoid odor of DMF that is used as a solvent for sucrose as a polymerization initiator (Japanese Patent Application Laid-open No. Hei 9(1997)-194588, Japanese Patent Application Laid-open No. Hei 10(1998)-81743, Japanese Patent Application Laid-open No. Hei 10(1998)-81744, etc.) and a method of using a phosphagen compound in order to avoid amine odor when amine is used as a polymerization catalyst (Japanese Patent Application Laid-open No. Hei 10(1998)-36499, Japanese Patent Application Laid-open No. Hei 11(1999)-60721, Japanese Patent Application Laid-open No. Hei 11(1999)-60722, etc.) have been proposed.
Of the odor of polyoxyalkylene polyol, aldehyde odor is unpleasant when using the polyoxyalkylene polyol, and besides, because of its inherent persistency, offensive odor clings to clothes after working. Further, urethane composition, its molded product, and the like using the polyoxyalkylene polyol also have the offensive odor. In particular, solution is urgently demanded to reduce aldehyde odor for the application in which a foamed urethane product is used in a closed space, as in the case of automotive upholsteries.
It is known that aldehyde is by-produced by oxidation of alkylene oxide which is a synthetic raw material of polyoxyalkylene polyol, and in some cases the aldehyde may be contained in the raw material alkylene oxide in the order of several to several tens ppm. Further, a method is proposed to suppress formation of aldehyde when producing polyoxyalkylene polyol. For example, it is proposed to use carbonate or bicarbonate of cesium as a polymerization catalyst in order to avoid alkali corrosion of alkylene oxide due to an alkali metal (Japanese Patent Application Laid-Open No. Hei 7(1995)-316284). Furthermore, in the production of polyoxyalkylene polyol using the phosphagen compound as a catalyst, it is proposed to control oxygen density together with addition of an antioxidant at purification in order to suppress formation of aldehyde and peroxide when purifying (vacuum treatment) a crude polyoxyalkylene polyol obtained by polymerization.
However, most of commercially available polyoxyalkylene polyols still have aldehyde odor.
The present invention has been made in view of the above prior art, and an object of the present invention is therefore to provide a low odor polyoxyalkylene polyol, a process for producing the low odor polyoxyalkylene polyol and a low odor urethane composition using the low odor polyoxyalkylene polyol as a raw material.
As a result of extensive investigations to obtain polyoxyalkylene polyol having low aldehyde odor, it has been found that a low odor polyoxyalkylene polyol is easily obtained by adding an amine having a specific structure to polyoxyalkylene polyol, and that, when this polyoxyalkylene polyol is used as a production raw material, a urethane composition which has low odor and which is not influenced by the amine is obtained. The present invention has been completed based on those findings.
A low odor polyoxyalkylene polyol according to the present invention comprises polyoxyalkylene polyol with amine added thereto, the amine having at least one amino group represented by the following formula (1): 
wherein R1, R2 and R3 independently represent hydrogen atom or an organic group which may contain a hetero atom in which an atom bonded to nitrogen atom is carbon atom.
The added amount of the above amine to the polyoxyalkylene polyol is generally 10,000 ppm or less.
Of R1, R2 and R3 in the above formula (1), it is preferable that at least one of those is hydrogen atom and at least one of those is an aliphatic hydrocarbon group which may contain hetero atom and/or aromatic group.
An amine containing at least one primary amino group in which any two of R1, R2 and R3 are hydrogen atoms is particularly preferable in the present invention.
Further, an amine containing a single amino group described above, i.e., monoamine, is also preferable.
The amine has preferably a boiling point of 100xc2x0 C. or higher under ordinary pressure.
The above-described low odor polyoxyalkylene polyol can be obtained by, for example, adding the amine represented by the above formula (1) to polyoxyalkylene polyol obtained by polymerization of oxyalkylene, and heating the resulting mixture under reduced pressure.
The present invention also provides a low odor urethane prepolymer using the above polyoxyalkylene polyol as a raw material, and a low odor urethane composition containing the urethane prepolymer. Since the amine reacts at the synthesis of the urethane prepolymer, amine derived from the low odor polyoxyalkylene polyol does not remain in the urethane prepolymer and the urethane composition containing the same.